OVERALL OBJECTIVES: The objective of the proposed research is to examine the regulation and the biochemical behavior of several folate metabolizing enzymes derived from human cells in culture in order to develop new chemotherapeutic approach for cancer treatment. The enzymes to be included in the study are TMP synthetase (TS), dihydrofolate reductase (DFR) and the 5,10 CH2H4 PteGlu Dehydrogenase-5,10 CH double bond H4 PeteGlu Cyclohydrolase -10 CHO H4PteGlu Synthetase Complex (DCS). The interaction of the enzymes with each other and with various forms of folypolyglutamate derivatives or folate analogs will be examined. The regulation of those enzyme activity inside cells will also be studied.